. The Femto Duo is a two-in-one safety light integrated into a versatile helmet mount. This light set features a front and rear light coupled by a composite matrix junction that’s compatible with nearly all vented-style helmets. The LEDs are in a super compact, lightweight and durable machined aluminium body The high-grade polycarbonate lenses provide side visibility and double as the power button. The front emits 15 Lumens, while the rear puts out 7 Lumens. Both front and rear lights feature three different output modes With easy to replace CR2032 batteries, the Femto Duo is a simple front and rear lighting system for increased night time visibility Features: Max Lumens: 15Run Time: 60hrs Modes: 5Battery: CR2032Buy Lezyne Accessories from Chain Reaction Cycles, the World’s Largest Online Bike Store.